1. Field Of The Invention
This invention relates to cathode ray tubes (CRT's) and more particularly to deflection limiting means for the resilient supports of a multi-opening electrode member positioned adjacent to the screen of the tube.
2. Description Of The Prior Art
Cathode ray tubes, such as those commonly utilized in color television and related display applications, conventionally employ a multi-opening structure, such as a shadow mask, positioned within the tube's viewing panel in spatial relationship to a patterned screen disposed on the interior surface of the panel.
The mask features a multi-apertured portion surrounded by a peripheral skirt, and is attached to the perimetrical wall of a supporting frame. This mask-frame assembly is supported by a plurality of elongated resilient support means located to mate with positioning studs embedded in and protruding from the sidewall of the panel.
Each of such mask-frame support means is conventionally formed by incorporating a transverse transitional bend into an elongated metallic spring member to demarcate a rigid basal seating portion and a longer arm-like resilient portion having a terminally-related stud-accepting aperture formed therein. Being thus formed, the two portions evidence an obtuse angular relationship when viewed along the bend axis. Thus, the seating portion, when suitably attached to the wall of the supporting frame, positions the resilient portion outwardly in a desired acute angular relationship with the frame.
To insert the mask-frame assembly into the panel, or to remove it, it is necessary to simultaneously move the several resilient portions of the respective support means inwardly toward the wall of the frame to clear the mating studs protruding from the panel sidewall. Such is accomplished by applying inwardly directed pressure against the resilient portions to achieve flexing of the resilient portions. Application of such pressure, exerts a stress on the transitional bends and seating portions of the support means. During this operation, the resilient portion often "bottoms out", meaning that the free end comes in contact with the wall of the frame or the sidewall of the mask. Since the mask is inserted into and removed from the panel several times during CRT fabrication, it has been found that repetitive bottoming-out of the support means tends to weaken or even deform the transitional bends therein, increasing the obtuse angle between the seating and resilient portions. Any deformation or flattening of the transitional bends, however small, results in a reduction of the spring bias of the individual support means against their respective studs. Such deformation of one or all of the support means may allow the mask to shift position relative to the patterned screen, deleteriously affecting image quality on the screen during CRT operation.
The terminal section of the resilient portion, when bottomed out, can also make contact with and damage the edge of the fragile apertured portion of the mask. This can occur when the support means are affixed on the mask frame at an acute angle to the edges of the frame, so that the resilient portions extend beyond the edges of the frame to positions adjacent to the edges of the apertured portion of the mask.